The daughter of acclaimed scientist Mary White has been found guilty of manslaughter over the death of her 92-year-old mother in an aged care home in 2018.

Barbara Eckersley never denied adding so called “green dream” drugs to her mother’s soup, but said she did not intend to kill her.

The NSW Supreme Court jury deliberated for just under three days before handing down its verdict on Thursday morning.

It found Eckersley was not guilty of murder, but the lesser charge of manslaughter, after the court heard she had been depressed about her mother’s ill health.

It heard the once lively and engaging scientist had been in a poor state before her death, with dementia causing her to be unable to speak and only able to consume liquid food.

She was about to be moved to another aged care home at Coffs Harbour after Eckersley differed with the home over her care.

Conservationist and palaeobotanist Mary White died in a nursing home in 2018. Photo: ABC

Trial hears of tension between Eckersley and nursing home staff

A key issue during the trial was the tension between the Eckersley family and nursing home staff over Dr White’s treatment.

The jury was shown a video Eckersley filmed that showed her mother in a distressed and agitated state.

She had wanted staff to make her more comfortable, but claimed there was resistance.

Prosecutor Paul Kerr told the jury it had got to a point where the staff thought they could never satisfy Eckersley’s expectations.

Eckersley claimed she was told by staff there was nothing more the home could do for her mother, and if she was not satisfied she could move Dr White elsewhere.

During the trial, it was revealed that the day before her mother’s death Eckersley had put eight crushed Temazapam tablets in Dr White’s dessert.

The stone mortar and pestle used to crush the tablets was passed to the jury.

The next day, Eckersley put eight to 10 millilitres of pentobarbital – also known as pentobarbitone or what is known as “green dream” drugs – into a takeaway sauce container, and took it to her mother’s home.

She told the court she had the drugs leftover from when she was a wildlife carer in Canberra more than two decades earlier.

She admitted to putting the drugs into her mother’s soup, motivated by a desire to help Dr White get a peaceful sleep.

Shortly afterwards, her mother began to cough, at which point Eckersley pushed an emergency buzzer and called for help.

Dr White died four hours later.

Eckersley told the jury she had been so affected by grief she had forgotten about the drugs.

She did not mention putting them in the soup in her initial police interview, only confessing a day or so later when the memory gradually returned.

“I was awake all night thinking about this and I just thought, Mum, if I don’t confess now, it’s going to make it look like Richard (her husband) involved,” she said in a police interview.

But Prosecutor Paul Kerr told the jury Eckersley’s story did not stack up.

“The claim that she had forgotten that she had mixed pentobarbitone into her mother’s meal before feeding her is just a lie,” he said.

Mr Kerr said the confession came only when Barbara Eckersley knew there would be an autopsy.

“You knew what you were doing was wrong,” he said.

“I knew I was giving her unprescribed medication, but my aim was not to kill her,” Eckersley replied.

The jury agreed, and Eckersley walked away from court after they found her guilty of manslaughter only.

She will be sentenced on May 20.

-ABC